Make declarative config YAML parsing and object mapping requirements pluggable via SPI

[jack-berg]

For declarative config is affected. I think a good way to do this is to make the task of taking parsing YAML and/or converting to pojo pluggable via SPI.

Roughly, the process looks like:

Object parsedYaml = org.snakeyaml.engine.v2.api.Load.loadFromInputStream(InputStream);
OpenTelemetryConfigurationModel model = com.fasterxml.jackson.databind.ObjectMapper.convertValue(parsedYaml, OpenTelemetryConfigurationModel.class);
OpenTelemetrySdk openTelemetrySdk = create(model);

So things we need to be pluggable:

• Parsing YAML InputStream to Object
• Converting Object to POJO

The serialization stuff in the unsupported OTLP json path adds more complexity since the API surface area of JsonSerializer is large.

Originally posted by @jack-berg in #8533

[jack-berg]

Assigning to myself or any other @open-telemetry/java-approvers interested. No external contributions on this one please.